A surgical instrument may be used to apply tension to a flexible suture to close and secure a broken or cut bone (e.g. a sternum following a sternotomy). The device preferably applies an adjustable tension to the flexible suture in order to secure the bone together. Multiple instruments may be used together to ensure the desired tension is applied to the entire bone structure being secured with the flexible sutures. Once the desired tension is achieved, the device preferably provides a mechanism to apply a uniform twist to the flexible suture to lock the flexible suture in place. The instrument preferably decreases the upward tension applied to the flexible sutures over the duration of the application of twisting. The device may automatically cut the flexible suture, or the flexible suture may be cut by the surgeon once the twisting action has been performed.